So today, I decided to put a home theater set-up mic in one of the cups and test the frequency response of my HD600's and make some small EQ compensations. The result? Perfectly flat across the spectrum except for the bass. Bass roll-off is completely normal to some degree but the roll-off here starts from like 90Hz. By 30Hz, the roll-off is pretty severe and a listening test confirmed this. I used RoomEQ to properly compensate for the roll-off but maybe they just need an amp like everyone says they do..

This is particularly strange, considering the HD600 is known for an excess of bass rather than a lack thereof. When comparing to the Headroom graph I found that my setup 'sounded' completely different.

So.. could it be that the Essence doesn't have enough juice to power the HD600 properly?

So today, I decided to put a home theater set-up mic in one of the cups and test the frequency response of my HD600's and make some small EQ compensations. The result? Perfectly flat across the spectrum except for the bass. Bass roll-off is completely normal to some degree but the roll-off here starts from like 90Hz. By 30Hz, the roll-off is pretty severe and a listening test confirmed this. I used RoomEQ to properly compensate for the roll-off but maybe they just need an amp like everyone says they do..

This is particularly strange, considering the HD600 is known for an excess of bass rather than a lack thereof. When comparing to the Headroom graph I found that my setup 'sounded' completely different.

So.. could it be that the Essence doesn't have enough juice to power the HD600 properly?

I cant comment on the power aspect of the hd600. Note that the headroom graph is taken on a dummy head. Your head may be a completely different shape and that will affect the result of the sound (particularly bass and highs based on seal etc).
As for the EQ, I dont think the HD600 really needs much to be relatively neutral (the highs could do with a boost if anything) and then the bass moved up.
The HD600 isnt known for an excessive amount of bass and it actually shys compared to its competition save for the k701 (i.e. the 650 and 880). Here I think you are confusing it with the 880 <- this should say 650 sorry :P.
The roll-off is a natural part of the 600 from what I remember. You may not need an amp, but I'd like to suggest you get one anyway

I can't understand how "excess" bass correlates with "early roll-off". Excess bass typically means there's a peak\hump somewhere in the mid- or highbass area. The lack of early roll-off usually called "deep bass". So, there's no condradictions here.
Apart from HD 600 doesn't have excessive bass and it goes pretty deep for an open can. It still audible under 30hz, how many open headphones can do that?

Whatever gave you the impression that the HD600 has the reputation for excess of bass? If anything, the HD600 has a reputation for a very polite, refined bass. And the bass extension is one of the few areas where the HD650 clearly improves upon the HD600.

@QQQ: The early roll-off, starting at around 90-100Hz results in fairly poor bass reproduction, hence the lack of adequate bass. This is based upon my experiences with calibrated home theater set-ups, as well as of course having measured the frequency response of my HD600. Headroom's graph (http://graphs.headphone.com/graphCom...=0&graphID=573) seems to have a big mid-bass hump and their measurements show a more 'shallow' roll-off, whereas for me the the low end is the problem, it's still audible but is significantly quieter in both measurements and my ear. When compensating with a software equalizer the response was much more flat but I don't find this to be an adequate solution..

@scytheavatar: The HD600 has a reputation for being dark, though not as dark as its HD650 brother.

EDIT: Here are my measurements:

After some more parametric EQ modifications I think I've gotten the HD600 to a place I like now Eliminated that one large peak at ~3KhZ that makes me twitch sometimes and put some minor boosts in the lower end (2-3dB) to ease the roll-off.

A bit of a happy ending I suppose, and a suggestion for anyone looking to softmod their cans a little bit, not to be afraid to try this themselves.

taso89.. Assuming these impedance measurements from HeadRoom are correct, here's the reason the HD600 lacks the lowest octaves (as do most open cans IME):

..This also corresponds perfectly to your own measurement. Also, notice how the ridge at 3-4 KHz corresponds to the peak you mentioned in your measurement. A CSD plot would likely show a nasty resonance in this area. I don't think this type of performance is the least bit uncommon with headphones though. I just received a set of HD600's in the last week btw.

That bump at 3-4khz explains why it has been so tricky for me to tune my vintage headphones after the HD580. I has been quite impossible to get that bump.... I now realize I should have looked at the HD580 graph... since the bump might not be a good thing.

taso89.. Assuming these impedance measurements from HeadRoom are correct, here's the reason the HD600 lacks the lowest octaves (as do most open cans IME):

..This also corresponds perfectly to your own measurement. Also, notice how the ridge at 3-4 KHz corresponds to the peak you mentioned in your measurement. A CSD plot would likely show a nasty resonance in this area. I don't think this type of performance is the least bit uncommon with headphones though. I just received a set of HD600's in the last week btw.

Few things.
Someone stated that the 600 is audible at 30 hz (i have to agree). Thats not even one octave it is missing.
as for the graph, that graph shows nothing as to why it would miss "lower octaves". Wont touch the rest of your post given the large thread you made filled with misinformation. That graph has little to do with the slight rolloff (which is more a side-effect of an open headphone than the impedence spike at 112 hz or so which is common among a lot of headphones). Do some research please..